1. Harmonizing microstructures and enhancing mechanical resilience : novel powder metallurgy approach for Zn–Mg alloysAnna Boukalová, Jiří Kubásek, David Nečas, Peter Minárik, Črtomir Donik, Drahomír Dvorský, Dalibor Vojtěch, Alena Michalcová, Matjaž Godec, Irena Paulin, 2024, original scientific article Abstract: Zinc alloys are recognised for their excellent biocompatibility and favourable corrosion rates, making them suitable for bioabsorbable implants. However, their mechanical properties necessitate improvement to fulfil the rigorous requirements of biomedical applications. This research focuses on engineering pseudo-harmonic structures within zinc alloys through a comprehensive method combining mechanical alloying, spark plasma sintering, and hot extrusion techniques. This fabrication process results in a composite material characterised by a soft core surrounded by a continuous, three-dimensional, ultrafine-grained hard shell. The experiment involved blending pure zinc with Zn–1Mg alloy powder, leading to the formation of both ductile zinc and fine-grained Zn–1Mg regions. While the Mg2Zn11 intermetallic phase was found to enhance the alloy's mechanical strength, the presence of oxide shells adversely affected the material's properties. The elimination of these shells via hot extrusion markedly improved the alloy's tensile strength, reaching an average value of tensile strength of 333 ± 7 MPa. This study provides significant insights into the material engineering of zinc-based alloys for biodegradable implant applications, demonstrating a viable approach to optimising their mechanical performance.
Keywords: zinc, magnesium, biodegradable, powder metallurgy, harmonic structure
Published in DiRROS: 23.07.2024; Views: 3; Downloads: 2
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2. Microstructural, corrosion and mechanical properties of a WE43 alloy : conventional extrusion versus SPDAnna Dobkowska, Aleksandra Zielińska, Irena Paulin, Črtomir Donik, Milena Koralnik, Bogusława Adamczyk-Cieślak, Monika Wieczorek-Czarnocka, Dariusz Kuc, Jiří Kubásek, Tomasz Mikuszewski, Matjaž Godec, Jarosław Mizera, 2024, original scientific article Abstract: A hexagonal close-packed-structure WE43 alloy was extruded without any preheating of the initial billet using extrusion with an oscillating die to improve the corrosion and mechanical properties. The WE43 alloy was extruded at high ratios of R 1 5:1, R 2 7:1 and R 3 10:1. Electron back-scatter diffraction and transmission electron microscopy were used to determine the microstructural properties of the alloys. The influence of the extrusion method and the extrusion ratios on the corrosion and mechanical properties were investigated. Electrochemical tests were performed, and the corrosion damage was inspected. Tensile tests were made using micro specimens. When compared to conventional extrusion, the microstructural changes obtained with the KoBo method at R 5:1 increased the corrosion resistance, which was not only due to the grain refinement, but also due to the intensity of the texture. A decline in the corrosion resistance of the alloys deformed at higher extrusion ratios was observed. This was a result of the massive plastic strain imposed by the KoBo die. The room-temperature mechanical properties of the KoBo-extruded alloys were improved. However, at higher temperatures the mechanical properties decreased due to the solutioning of tiny triple precipitates.
Keywords: WE43, several plastic deformation, microstructure, corrosion, mechanical properties
Published in DiRROS: 23.07.2024; Views: 1; Downloads: 0
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3. Exploring the microstructure, mechanical properties, and corrosion resistance of innovative bioabsorbable Zn-Mg-(Si) alloys fabricated via powder metallurgy techniquesDavid Nečas, Vojtěch Hybášek, Jan Pinc, Andrea Školáková, Ilona Voňavková, Klára Hosová, Martin Zlámal, Anna Boukalová, Jan Pokorný, Drahomír Dvorský, Črtomir Donik, Dalibor Vojtěch, Jiří Kubásek, 2024, original scientific article Abstract: Zinc alloys belong to the widely studied materials for applications like medical devices, however, they often
encounter an inappropriate combination of mechanical/corrosion/biological properties. In this respect, we
produced the Zn–1Mg and Zn–1Mg–1Si containing biologically friendly elements with potential strengthening
effects on zinc matrix by powder metallurgy methods including mechanical alloying, spark plasma sintering, and
extrusion further enabling the formation of materials with unique extremely fine-grained microstructures. The
systematic study of these materials showed the possibility of reaching homogeneous nano-grain microstructure
and high strength values exceeding 450 MPa in tension. Selected chemical composition and processing methods
led also to slightly decreased wear and corrosion rates and rather uniform corrosion.
Keywords: zinc, mechanical alloying, biodegradable metals, composite, spark plasma sintering, extrusion, powder metallurgy
Published in DiRROS: 23.07.2024; Views: 1; Downloads: 2
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4. Diagnostic performance of p16/Ki-67 dual immunostaining at different number of positive cells in cervical smears in women referred for colposcopyUršula Salobir Gajšek, Andraž Dovnik, Iztok Takač, Urška Ivanuš, Tine Jerman, Simona Šramek Zatler, Alenka Repše-Fokter, 2021, original scientific article Abstract: . The aim of the study was to evaluate the diagnostic accuracy of p16/Ki-67 dual immunostaining (p16/ Ki-67 DS) in cervical cytology and the number of positive p16/Ki-67 cells to diagnose high grade cervical intraepithelial neoplasia (CIN2+) in colposcopy population. Subjects and methods. We performed an analysis on a subset cohort of 174 women enrolled within a large-scale randomised controlled human papillomavirus (HPV) self-sampling project organised as part of the population-based Cervical Cancer Screening Programme ZORA in Slovenia. This subset cohort of patients was invited to the colposcopy clinic, underwent p16/Ki-67 DS cervical cytology and had the number of p16/Ki-67 positive cells determined. Results. Among analysed women, 42/174 (24.1%) had histologically confirmed CIN2+. The risk for CIN2+ was increasing with the number of positive cells (p < 0.001). The sensitivity of p16/Ki-67 DS for detection of CIN2+ was 88.1%, specificity was 65.2%, positive predictive value was 44.6% and negative predictive value was 94.5%. Conclusions. Dual p16/Ki-67 immunostaining for the detection of CIN2+ has shown high sensitivity and high negative predictive value in our study, which is comparable to available published data. The number of p16/Ki-67 positive cells was significantly associated with the probability of CIN2+ detection. We observed a statistically significant and clinically relevant increase in specificity if the cut-off for a positive test was shifted from one cell to three cells.
Keywords: cervical cytology, high-grade dysplasia, p16/Ki-67 immunostaining
Published in DiRROS: 22.07.2024; Views: 29; Downloads: 5
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5. MitomiRs: their roles in mitochondria and importance in cancer cell metabolismAndrej Renčelj, Nada Gvozdenović, Maja Čemažar, 2021, review article Abstract: Background. MicroRNAs (miRNAs) are short non-coding RNAs that play important roles in almost all biological path- ways. They regulate post-transcriptional gene expression by binding to the 3%untranslated region (3%UTR) of messenger RNAs (mRNAs). MitomiRs are miRNAs of nuclear or mitochondrial origin that are localized in mitochondria and have a crucial role in regulation of mitochondrial function and metabolism. In eukaryotes, mitochondria are the major sites of oxidative metabolism of sugars, lipids, amino acids, and other bio-macromolecules. They are also the main sites of adenosine triphosphate (ATP) production. Conclusions. In the review, we discuss the role of mitomiRs in mitochondria and introduce currently well studied mito- miRs, their target genes and functions. We also discuss their role in cancer initiation and progression through the regu- lation of mRNA expression in mitochondria. MitomiRs directly target key molecules such as transporters or enzymes in cell metabolism and regulate several oncogenic signaling pathways. They also play an important role in the Warburg effect, which is vital for cancer cells to maintain their proliferative potential. In addition, we discuss how they indirectly upregulate hexokinase 2 (HK2), an enzyme involved in glucose phosphorylation, and thus may affect energy metabo- lism in breast cancer cells. In tumor tissues such as breast cancer and head and neck tumors, the expression of one of the mitomiRs (miR-210) correlates with hypoxia gene signatures, suggesting a direct link between mitomiR expression and hypoxia in cancer. The miR-17/92 cluster has been shown to act as a key factor in metabolic reprogramming of tumors by regulating glycolytic and mitochondrial metabolism. This cluster is deregulated in B-cell lymphomas, B-cell chronic lymphocytic leukemia, acute myeloid leukemia, and T-cell lymphomas, and is particularly overexpressed in several other cancers. Based on the current knowledge, we can conclude that there is a large number of miRNAs present in mitochondria, termed mitomiR, and that they are important regulators of mitochondrial function. Therefore, mitomiRs are important players in the metabolism of cancer cells, which need to be further investigated in order to develop a potential new therapies for cancer.
Keywords: microRNAs, mitomiR, mitochondria, cancer cell metabolism
Published in DiRROS: 22.07.2024; Views: 34; Downloads: 6
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7. Recycling of different incineration ashes in the construction sector : perspectives from SloveniaVesna Zalar Serjun, 2024, original scientific article Abstract: The EU prioritizes transitioning to a circular economy, aiming to boost sustainable resource management through policies promoting recycling and reuse, benefiting both the environment and the economy. Many successful case studies demonstrate using various incineration waste by-products (ashes) as substitutes for natural materials, yielding environmental advantages and showcasing sustainable resource management practices. While extensive literature covers ash characterization and applications, the direct links between the properties of the main components, the amorphous phase, and research findings remain elusive. Analysis predominantly centers on microstructural phase development, influencing mechanical, physical, and chemical properties and guiding research interpretations. Existing standards for ash use primarily address coal-derived fly ash, with SIST EN 13282-2 allowing alternative sources like circulating fluidized bed and paper sludge incineration residues. Yet, beyond this standard, no regulations mandate using different ash types. Nonetheless, the applicability of ashes for the geotechnical composite materials has already been confirmed in the field since numerous geotechnical projects have been carried out in Slovenia. Such composites have been recognized as beneficial practices, and the majority of them also possess legal permission for usage according to the Slovenian Technical Approvals. Given the varying value and complexity of ashes, detailed characterization before use is crucial. Assessing the recycling potential of different ashes requires a precise definition of basic properties such as microstructure, minerals, and chemical composition. Emphasis should be placed on characterizing the hydraulic properties and gaining detailed insights into the amorphous phase, ensuring informed decision-making regarding their recycling processes.
Keywords: waste by-products from incineration processes, ashes, recycling, amorphous phase, (latent) hydraulic properties, hydration
Published in DiRROS: 22.07.2024; Views: 26; Downloads: 10
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8. Simvastatin is effective in killing the radioresistant breast carcinoma cellsBertram Aschenbrenner, Giulia Negro, Dragana Savic, Maxim Sorokin, Anton A. Buzdin, Ute Maria Ganswindt, Maja Čemažar, Gregor Serša, Sergej Skvortsov, Ira Skvortsova, 2021, original scientific article Abstract: Background. Statins, small molecular 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, are widely used to lower cholesterol levels in lipid-metabolism disorders. Recent preclinical and clinical studies have shown that statins exert beneficial effects in the management of breast cancer by increasing recurrence free survival. Unfortunately, the underlying mechanisms remain elusive. Materials and methods. Simvastatin, one of the most widely prescribed lipophilic statins was utilized to investigate potential radiosensitizing effects and an impact on cell survival and migration in radioresistant breast cancer cell lines. Results. Compared to parental cell counterparts, radioresistant MDA-MB-231-RR, T47D-RR andAu565-RR cells were characterized by upregulation of 3-hydroxy-3-methylglutharyl-coenzyme A reductase (HMGCR) expression accom-panied by epithelial-to-mesenchymal transition (EMT) activation. Radioresistant breast cancer cells can be killed by simvastatin via mobilizing of a variety of pathways involved in apoptosis and autophagy. In the presence of simvasta-tin migratory abilities and vimentin expression is diminished while E-cadherin expression is increased. Conclusions. The present study suggests that simvastatin may effectively eradicate radioresistant breast carcinoma cells and diminish their mesenchymal phenotypes.
Keywords: radiotherapy, breast cancer, radioresistant cells
Published in DiRROS: 22.07.2024; Views: 26; Downloads: 10
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9. Lastnosti lesa iz rudnika SitarjevecMiha Humar, Boštjan Lesar, Davor Kržišnik, Andreja Pondelak, Andrijana Sever Škapin, Angela Balzano, José Gonçalves, 2024, original scientific article Abstract: Rudarska tradicija v Litiji, segajoča v staro železno dobo, je vključevala intenzivno uporabo lesa v rudnikih, še posebej za podporo in zaščito rovov. Rudnik Sitarjevec je bil znova odprt za turizem leta 2017, in v letu 2021 so odprli glavni rov. Les ostaja ključen material v rudnikih, čeprav so ga v preteklosti nadomeščali z drugimi materiali. Uporabljeni les je izpostavljen razkroju zaradi visoke vlažnosti in gliv, kot je bela hišna goba. Ta gliva lahko povzroči razgradnjo lesa in je pogosta v vlažnih okoljih rudnikov. Obstoj gliv je pomemben, saj lahko vplivajo na obiskovalce rudnika. Visoka relativna zračna vlažnost (96,6 %) in stalna temperatura (10,1 °C) v rudniku ustvarjata razmere, ki so ugodne za rast gliv, vendar pa relativno nizka temperatura ni omejujoč dejavnik za razgradnjo lesa. Koncentracija glivnih spor v rudniku je visoka in je razložena z razširjenostjo gliv v samem rudniku. Poleg tega smo opazili, da je v lesu veliko anorganskih onesnaževal ter veliko kristalov.
Keywords: razkroj, bela hišna goba, težke kovine, kristali, spore
Published in DiRROS: 22.07.2024; Views: 28; Downloads: 4
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10. A protocol for accurate radiochromic film dosimetry using Radiochromic.comIgnasi Méndez Carot, Juan José Rovira-Escutia, Božidar Casar, 2021, original scientific article Abstract: Radiochromic films have many applications in radiology and radiation therapy. Generally, the dosim-etry system for radiochromic film dosimetry is composed of radiochromic films, flatbed scanner, and film analysis soft-ware. The purpose of this work is to present the effectiveness of a protocol for accurate radiochromic film dosimetry using Radiochromic.com as software for film analysis.Materials and methods. Procedures for image acquisition, lot calibration, and dose calculation are explained and analyzed. Radiochromic.com enables state-of-the-art models and corrections for radiochromic film dosimetry, such as the Multigaussian model for multichannel film dosimetry, and lateral, inter-scan, and re-calibration corrections of the response.Results. The protocol presented here provides accurate dose results by mitigating the sources of uncertainty that affect radiochromic film dosimetry. Conclusions. Appropriate procedures for film and scanner handling in combination with Radiochromic.com as software for film analysis make easy and accurate radiochromic film dosimetry feasible.
Keywords: radiochromic film, dosimetry, protocol
Published in DiRROS: 22.07.2024; Views: 20; Downloads: 4
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